<html>
  <head><title>main frame</title></head>
  <body>
  <script>
    // Create an iFrame in response to a nudge by the test harness (in the form
    // of a posted message).
    window.addEventListener('message', function(event) {
      var iframe = document.createElement('iframe');
      iframe.src = "child_frame.html";
      iframe.onload = function() {
        document.title = 'iframe loaded';
      };
      document.body.appendChild(iframe);
    });
  </script>
  </body>
</html>
